Coding Agent

What This Demonstrates

Copilot coding agent implements features, applies cross-cutting changes, and fixes bugs — generating code that follows existing project conventions.

Prerequisites

• VS Code with Copilot Chat open
• Repository loaded with services running (docker-compose up -d)

Prompts

Prompt A — Small Implementation

Implement health/readiness endpoints for `services/payment-service` and add
unit tests for them, following existing code style and API response format.

What to look for:

• /health and /ready endpoints following the project’s response format
• Unit tests matching existing test structure and assertion style
• Proper TypeScript types from @octo-eshop/types

Prompt B — Cross-Cutting Change

Add standardized request ID propagation middleware to all backend services and
ensure logs include the request ID. Make minimal, consistent changes only.

What to look for:

• Consistent middleware implementation across all services
• Request ID in log output
• Minimal diff — no unnecessary refactoring

Prompt C — Bugfix Scenario

Find and fix one realistic input-validation gap in `services/order-service`
checkout flow. Add/adjust tests to prove the fix.

What to look for:

• Identified validation gap with explanation
• Surgical fix (not a rewrite)
• Tests that cover both the happy path and the edge case

Follow-Up Prompts

• “Now add integration tests for the health endpoints using supertest.”
• “Show me the diff summary of all changes made.”
• “Are there similar validation gaps in cart-service?”